Electrode system



May 2, 1939. w. c. VAN GEEL ,15

I ELECTRODE SYSTEM I I Y Filed June 20, 1936 I INVENTOR I W.,C. VAN GEEL i ATI[6RNEY Patented lillayz, 1939 i L I I UNITED STATES PATENT OFFICE ELECTRODE SYSTEM Willem Christiaan van Geel, Eindhoven, Netherlands, assignor to N. V. Philips Gloeilampenfabrieken, Eindhoven, Netherlands, a corporation of the Netherlands Application June 20, 1936, Serial No. 86,289 In Germany July 31, 1935 6 Claims; (Cl. 175-366) This invention relates to an electrode system for rately and is not formed together with the semirectifying or controlling high or intermediate freconductor by oxidation of the copper base, as it quency electrical oscillations, in which the posiis the casevwith cupro-oxide t t tive and negative electrodes consist of materials However, there are still other factors affecting having a V y e e t emitting p y with the capacity in an electrode system, viz. the respect to one another and being separated by a surface of, the highly emitting electrode, and the Solid insulating ayer. surface of the supply conductor for the semi- It has already been proposed to provide a conductor. conical lead contact on a graphite layer which is For this purpose it has already been-proposed used as a p y conductor in a upr s oxid with such systems, similarly as with crystal de 10 detector. In this case the capacity is determined tectors, to give the contact end of one ofthe conby the surface of the graphite layer bearing the ductive parts afi'ecting the capacity a small crossd Contact However, it is Very difficlllt to 1)- section, viz, a point. However, this form entails tain a small surface capable of being reproduced v rious difiiculties, more particularly while the with the aid Such a layerpoint may readily penetrate into the substratum Furthermore it is known that the detector may or damage it. Furthermore a correct arrangeconsist of a crystal; However, a crystal detector ment of the point is difficult. has a rectifying efiect On y at O e or a ew points According to the invention these drawbacks are i of the crystal surface and more particularly: avoided by surrounding the tapering end with in- I here the surface bears an insulating c a vsulating material which in the plane of the contact ing such a thickness that its resistance does not end has a cross-section whose surface is many have an excessive value and corresponds to the times larger than that of the contact end. pp voltage to be ect fied. Thus, in order In a suitable form of construction the end of that a crystal can be used as a-detector the surthe conductor is given a conical shape, the top k face of the crystal must be ed With the aid being flattened so that a flat surface is obtained Of a Pointed metal act till a po t av ng a which is used as a contact, By means of a selffy n efiect W have been found. In this 'capacity'to be indicated for such an electrode case there s s qu nt y a s a sursystem said surface can be determined beforeface, viz. of the good conductive electrode on the hand.

insulating coating, it is true, but the thickness It will be clear that in this manner a perfect of the insulating coating cannot be fixed in an electrical connection is ensured, whereas there exact and reproducible manner, so that the cais no risk of the top of the conductor, which may pacity of such a detector cannot be controlled at be conical and has preferably a small surface not' exceeding 0.25 mm. being pressed through the The object of the invention is to provide an thinsemi-conductive layer or even through the electrode system having a small and reproinsulating coating which would cause a shortducible self-capacity which is of paramount imcircuit in the system.

portance with electrode systems used as a de- The difficulty that'a cone. having such a small tector or as a control member for high or intersurface cannot be kept upright without addit1onal mediate frequency oscillations. means on the surface of the semi-conductor, 1s 0 Indeed, the self-capacity of such a system exfurther disposed of by the large base formed by erts a certain influence on a circuit comprising the surrounding insulating material. In a suitthe cell. In order to ensure the maximum effect v able form of construction this material consists of in such a circuit definite measures should be a compound. I taken in designing it. If the various cells would However, it is advantageous to surround not have a different self-capacity with respect to only the'contact, but also the whole electrode each other then in spite of certain measures being system with casting material owing to which the taken the latter would be of no avail when the whole acquires a higher mechanical solidity. initial cell adapted to the circuit would bere- In the following form of construction of an placed by another one. electrode system according to the invention the The capacity depends, among other things, on semi-conductor 1 consists of selenium, which is the thickness of the insulating coating provided applied in the liquid state on a metal support 2 between the electrodes. In the systems referred consisting'for, instance, of brass and being used to above the thickness has a perfectly fixed value at the same time asa supply conductor for the since the insulating coating is arranged sepaselenium, which is smoothly painted up to a thickness of about 0.03 mm. The carrier, together with the selenium, is heated in a furnace for about 2 to 24 hours at about 200 in order to convert the selenium into the conductive crystalline modification. An insulating coating 3 consisting, for instance of polystyrene and having a thickness of 5;; is applied on to i the selenium.

The good conductive electrode which may consist of air iron rod 4 having a contact surface of 0.25 mm. at the bottom side, is embedded in a cubical or cylindrical body 5 of polystyrene or compound, at any rate of insulating material, whose bottom surface is at a level with the contact surface 6. The whole is provided on the insulating coating 3, the insulating envelope 5 being secured to the insulating coating 3 by means of an adhesive.

Also other forms of construction fall under the scope of the invention such as those comprising more than two electrodes, for instance, threeelectrode systems.

As an alternative the whole system represented in the drawing may, moreover, be surrounded with an insulating layer, so that it is free from external mechanical and atmospherical influences and owing to which, moreover, the supply wires experience much lower mechanical efforts at the welds of the electrodes.

What I claim is:

1. An electrode-system for rectifying or controlling high or intermediate frequency electrical oscillations, comprising positive and negative electrodes composed of iron and selenium, respectively, said electrodes being separated by a solid insulating coating of polystyrene, and wherein at least one of the electrodes influencing the capacity has a small cross-section at the contact end, this end being surrounded with insulating material whose cross-section in the plane of the contact endhas a surface whichis many times larger than that of the contact end.

7 2. An electrode system as claimed in claim 1 in which the end of the conducting'part influencing the capacity has a conical shape.

3. An electrode system as claimed in claim 1 in which the end of the conducting part influencing the capacity has a conical shape and in which the surface of the contact end does not exceec 0.25 mmfi.

4. An electrode system as claimed in claim 1 in which the selenium layer is applied on to a brass plate, said layer being furnished with-ar insulating coating of polystyrene which is provided at its free surface and on to which an iron counter electrode having a small contact surface (0.25 mm?) and being laterally surrounded b5 polystyrene is applied, the polystyrene envelope being mechanically secured to the insulating coating by means of an adhesive.

5. A contact rectifier electrode systemcomprising an eleotrodeof selenium having a relatively large plane surface, a thin layer of polystyrene pervious to the flow of electrons applied to said electrode surface, and a positive electrode of iron having a surface many times smaller than the first electrode surface contacting with said insulating layer.

6. A contact rectifier electrode system comprising an electrode of selenium having a relatively large plane surface, a thin layer of polystyrene pervious to the flow of electrons applied to said electrode surface, an insulating block having a plane surface substantially coextensive with the insulating layer and contactingtherewith, a positive electrode of iron in the form of a rod embedded within said insulating block, one end 01 the rod extending to the contacting surface of the block and having its surface of small area lying in the same plane as said contacting surface.

WILLEM CHRISTIAAN VAN GEEL. 

